better support for redhat 5 systems

- added custom fact sudoversion (currently supports rhel only)
- print warning message on rhel 5 if sudo version is < 1.7.2p1
- moved packge_ensure to params.pp and set it to latest for rhel 5.[01234]
- rspec test for rhel 5.4 to check of package_ensure is really latest
- anchor pattern for class sudo::package in class sudo